kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-10-16 22:39:48 +00:00
Code Issues Releases Packages Activity
No description
1,059,612 commits 116 branches 5,798 tags 5.6 GiB
  • C 96.9%
  • Assembly 0.9%
  • Rust 0.6%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Vitaly Kuznetsov 51500b71d5 x86/hyperv: Properly deal with empty cpumasks in hyperv_flush_tlb_multi() 
KASAN detected the following issue:

 BUG: KASAN: slab-out-of-bounds in hyperv_flush_tlb_multi+0xf88/0x1060
 Read of size 4 at addr ffff8880011ccbc0 by task kcompactd0/33

 CPU: 1 PID: 33 Comm: kcompactd0 Not tainted 5.14.0-39.el9.x86_64+debug #1
 Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine,
     BIOS Hyper-V UEFI Release v4.0 12/17/2019
 Call Trace:
  dump_stack_lvl+0x57/0x7d
  print_address_description.constprop.0+0x1f/0x140
  ? hyperv_flush_tlb_multi+0xf88/0x1060
  __kasan_report.cold+0x7f/0x11e
  ? hyperv_flush_tlb_multi+0xf88/0x1060
  kasan_report+0x38/0x50
  hyperv_flush_tlb_multi+0xf88/0x1060
  flush_tlb_mm_range+0x1b1/0x200
  ptep_clear_flush+0x10e/0x150
...
 Allocated by task 0:
  kasan_save_stack+0x1b/0x40
  __kasan_kmalloc+0x7c/0x90
  hv_common_init+0xae/0x115
  hyperv_init+0x97/0x501
  apic_intr_mode_init+0xb3/0x1e0
  x86_late_time_init+0x92/0xa2
  start_kernel+0x338/0x3eb
  secondary_startup_64_no_verify+0xc2/0xcb

 The buggy address belongs to the object at ffff8880011cc800
  which belongs to the cache kmalloc-1k of size 1024
 The buggy address is located 960 bytes inside of
  1024-byte region [ffff8880011cc800, ffff8880011ccc00)

'hyperv_flush_tlb_multi+0xf88/0x1060' points to
hv_cpu_number_to_vp_number() and '960 bytes' means we're trying to get
VP_INDEX for CPU#240. 'nr_cpus' here is exactly 240 so we're trying to
access past hv_vp_index's last element. This can (and will) happen
when 'cpus' mask is empty and cpumask_last() will return '>=nr_cpus'.

Commit ad0a6bad44 ("x86/hyperv: check cpu mask after interrupt has
been disabled") tried to deal with empty cpumask situation but
apparently didn't fully fix the issue.

'cpus' cpumask which is passed to hyperv_flush_tlb_multi() is
'mm_cpumask(mm)' (which is '&mm->cpu_bitmap'). This mask changes every
time the particular mm is scheduled/unscheduled on some CPU (see
switch_mm_irqs_off()), disabling IRQs on the CPU which is performing remote
TLB flush has zero influence on whether the particular process can get
scheduled/unscheduled on _other_ CPUs so e.g. in the case where the mm was
scheduled on one other CPU and got unscheduled during
hyperv_flush_tlb_multi()'s execution will lead to cpumask becoming empty.

It doesn't seem that there's a good way to protect 'mm_cpumask(mm)'
from changing during hyperv_flush_tlb_multi()'s execution. It would be
possible to copy it in the very beginning of the function but this is a
waste. It seems we can deal with changing cpumask just fine.

When 'cpus' cpumask changes during hyperv_flush_tlb_multi()'s
execution, there are two possible issues:
- 'Under-flushing': we will not flush TLB on a CPU which got added to
the mask while hyperv_flush_tlb_multi() was already running. This is
not a problem as this is equal to mm getting scheduled on that CPU
right after TLB flush.
- 'Over-flushing': we may flush TLB on a CPU which is already cleared
from the mask. First, extra TLB flush preserves correctness. Second,
Hyper-V's TLB flush hypercall takes 'mm->pgd' argument so Hyper-V may
avoid the flush if CR3 doesn't match.

Fix the immediate issue with cpumask_last()/hv_cpu_number_to_vp_number()
and remove the pointless cpumask_empty() check from the beginning of the
function as it really doesn't protect anything. Also, avoid the hypercall
altogether when 'flush->processor_mask' ends up being empty.

Fixes: ad0a6bad44 ("x86/hyperv: check cpu mask after interrupt has been disabled")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20220106094611.1404218-1-vkuznets@redhat.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
History 2022-01-10 11:50:20 +00:00
arch x86/hyperv: Properly deal with empty cpumasks in hyperv_flush_tlb_multi() 2022-01-10 11:50:20 +00:00
block block-5.16-2021-12-10 2021-12-11 09:25:07 -08:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto Update to zstd-1.4.10 2021-11-13 15:32:30 -08:00
Documentation Char/misc driver fixes for 5.16-rc5 2021-12-12 10:16:34 -08:00
drivers Drivers: hv: vmbus: Initialize request offers message for Isolation VM 2022-01-05 20:39:14 +00:00
fs Fixes for 5.16-rc4: 2021-12-11 16:21:06 -08:00
include Drivers: hv: Fix definition of hypercall input & output arg variables 2021-12-28 14:18:43 +00:00
init kbuild: Fix -Wimplicit-fallthrough=5 error for GCC 5.x and 6.x 2021-11-14 18:59:49 -08:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-11-20 10:35:54 -08:00
kernel swiotlb: Add CONFIG_HAS_IOMEM check around swiotlb_mem_remap() 2022-01-04 16:11:19 +00:00
lib Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2021-12-08 16:06:44 -08:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm Merge branch 'for-5.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu 2021-12-11 16:14:17 -08:00
net net/sched: fq_pie: prevent dismantle issue 2021-12-09 08:01:00 -08:00
samples ftrace/samples: Add module to test multi direct modify interface 2021-12-09 13:02:44 -05:00
scripts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid 2021-11-24 09:44:13 -08:00
security selinux: fix NULL-pointer dereference when hashtab allocation fails 2021-11-19 16:11:39 -05:00
sound sound fixes for 5.16-rc5 2021-12-10 11:43:00 -08:00
tools perf tools fixes for v5.16: 3rd batch 2021-12-11 13:28:02 -08:00
usr initramfs: Check timestamp to prevent broken cpio archive 2021-10-24 13:48:40 +09:00
virt KVM: downgrade two BUG_ONs to WARN_ON_ONCE 2021-11-26 06:43:28 -05:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update email address for Guo Ren 2021-12-10 17:10:55 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Char/misc driver fixes for 5.16-rc5 2021-12-12 10:16:34 -08:00
Makefile Linux 5.16-rc5 2021-12-12 14:53:01 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.